Cross-linked porous polymer separator using vinyl-modified aluminum oxide nanoparticles as cross-linker for lithium-ion batteries

Development of AlN-loaded PET separators from waste water bottle plastics with superior thermal characteristics for next-generation lithium-ion batteries

Preventing short circuit hazard due to lithium (Li) dendrite formation across a separator from the anode of a lithium-ion battery (LIB) throughout operation is important; however, conventional separator materials cannot fulfil the increasing safety standards of next-generation LIBs. Thus, developing separator materials with high Li dendrite suppression ability in order to prevent short circuit is of paramount importance for realising next-generation LIBs. In this study, aluminum nitride-loaded polyethylene terephthalate (PET/AlN) composites with micro-/nanoarchitecture were synthesized using PET that was recycled from commercial waste bottles via an electrospinning strategy. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) suggested that AlN nanoparticles were encapsulated in PET micro-/nanoarchitecture fibres. Thermogravimetric analysis indicated that the AlN content in the composite materials was about 4-5 wt%. X-ray photoelectron spectroscopy (XPS) and Fourier-transform infrared (FTIR) spectroscopy confirmed the PET polymer structure of PET/AlN composites. The PET/AlN 4 wt% separator exhibited a porosity of 69.23%, according to the n-butanol uptake test, and a high electrolyte uptake of 521.69%. Most importantly, electrochemical results revealed that when evaluated at a current density of 0.5C, PET/AlN 4 wt% composites could deliver a reversible specific capacity of 238.2 mA h g-1 after 100 cycles. When C-rate capability tests were conducted at high charge-discharge densities of 0.2, 0.5, 1, 2, and 4C, the PET/AlN 4 wt% composite manifested average specific capacities of about 225.3, 218.4, 191.0, 127.5, and 28.1 mA h g-1, respectively. The excellent electrochemical performance of the PET/AlN 4 wt% composite could probably be attributed to the combined benefits of AlN nanoparticles and the micro-/nanoarchitecture. These unique features of PET/AlN were advantageous for effective Li ion transport in repeated charge-discharge cycles and strong hydrothermal stability, thereby resulting in safety, high capacity and excellent C-rate performance. Overall, this study demonstrated the excellent electrochemical performance of PET/AlN composites as stable separator materials for advanced LIBs.

Enhanced ionic conductivity and electrochemical performance of environmental friendly guar gum-based bio polymer gel electrolytes doped with Al2O3 nanofibers for Li-ion batteries

Recently, biopolymers made from natural resources are gaining popularity as polymer electrolytes (PEs) in electrochemical devices. In the present work, a series of guar gum (GG)-based biopolymer gel electrolytes (BGEs) filled with different amounts of Al2O3 nanofibers are synthesized and tested. The BGEs containing 7.5 wt% Al2O3 nanofibers show the maximum room temperature ionic conductivity of 2.37 × 10-3 S/cm at an uptake ratio of 120 %. Given the high conductivity, this uptake ratio is low, demonstrating that Al2O3 nanofibers affect GG's ion transport characteristics. XRD reveals that the Al2O3 in GG can create conductive environment for ion conduction. FTIR and XPS analyses demonstrate that nanofibers have the ability to generate supplementary routes for ion conduction in GG. Electrochemical investigations show that BGEs with 7.5 wt% nanofibers have a broad electrochemical potential range of 4.6 V. BGEs are stable at metallic electrodes and have a cationic transference number of 0.59. The initial discharge capacity at 0.5C has been measured to be 127 mAh g-1 for Li|BGE|LiFePO4 cell in the first cycle and 116 mAh g-1 with coulombic efficiency of over 94 % after 100 cycles. Nanofiber-dispersed BGEs have high thermal and mechanical stabilities, according to TGA, DSC, and UTM tests.

Boosting Thermal and Mechanical Properties: Achieving High-Safety Separator Chemically Bonded with Nano TiN Particles for High Performance Lithium-Ion Batteries

Currently, the commercial separator (Celgard2500) of lithium-ion batteries (LIBs) suffers from poor electrolyte affinity, mechanical property and thermal stability, which seriously affect the electrochemical performances and safety of LIBs. Here, the composite separators named PVDF-HFP/TiN for high-safety LIBs are synthesized. The integration of PVDF-HFP and TiN forms porous structure with a uniform and rich organic framework. TiN significantly improves the adsorption between PVDF-HFP and electrolyte, causing a higher electrolyte absorption rate (192%). Meanwhile, XPS results further demonstrate the tight link between PVDF-HFP and TiN due to the existence of TiF bond in PVDF-HFP/TiN, resulting in a strong impediment for the puncture of lithium dendrites as a result of the improved mechanical strengths. And PVDF-HFP/TiN can effectively suppress the growth of lithium dendrites by means of uniform lithium flux. In addition, the excellent heat resistance of TiN improves the thermal stability of PVDF-HFP/TiN. As a result, the LiFePO₄ ||Li cells assembled PVDF-HFP/TiN-12 exhibit excellent specific capacity, rate performance, and capacity retention rate. Even the high specific capacity of 153 mAh g^-1 can be obtained at the high temperature of 80 °C. Meaningfully, a reliable modification strategy for the preparation of separators with high safety and electrochemical performance in LIBs is provided.

Experimental and computational investigation on the charge storage performance of a novel Al2O3-reduced graphene oxide hybrid electrode

The advancements in electrochemical capacitors have noticed a remarkable enhancement in the performance for smart electronic device applications, which has led to the invention of novel and low-cost electroactive materials. Herein, we synthesized nanostructured Al₂O₃ and Al₂O₃-reduced graphene oxide (Al₂O₃-rGO) hybrid through hydrothermal and post-hydrothermal calcination processes. The synthesized materials were subject to standard characterisation processes to verify their morphological and structural details. The electrochemical performances of nanostructured Al₂O₃ and Al₂O₃- rGO hybrid were evaluated through computational and experimental analyses. Due to the superior electrical conductivity of reduced graphene oxide and the synergistic effect of both EDLC and pseudocapacitive behaviour, the Al₂O₃- rGO hybrid shows much improved electrochemical performance (~ 15-fold) as compared to bare Al₂O₃. Further, a symmetric supercapacitor device (SSD) was designed using the Al₂O₃- rGO hybrid electrodes, and detailed electrochemical performance was evaluated. The fabricated Al₂O₃- rGO hybrid-based SSD showed 98.56% capacity retention when subjected to ~ 10,000 charge-discharge cycles. Both the systems (Al₂O₃ and its rGO hybrid) have been analysed extensively with the help of Density Functional Theory simulation technique to provide detailed structural and electronic properties. With the introduction of reduced graphene oxide, the available electronic states near the Fermi level are greatly enhanced, imparting a significant increment in the conductivity of the hybrid system. The lower diffusion energy barrier for electrolyte ions and higher quantum capacitance for the hybrid structure compared to pristine Al₂O₃ justify improvement in charge storage performance for the hybrid structure, supporting our experimental findings.

Development of Cotton Fabrics via EVA/SiO2/Al2O3 Nanocomposite Prepared by γ-Irradiation for Waterproof and Fire Retardant Applications

Development of cotton fabric (CF) properties using nanocomposites via coating method was of considerable interest for wide applications. This article aims at developing CF properties by coating treatment using ethylene–vinyl-acetate (EVA), silicon dioxide (SiO2), aluminum oxide (Al2O3) nanoparticles and γ-irradiation widely used in waterproof and flame retardant applications. EVA-based nanocomposites, EVA/SiO2, EVA/Al2O3, and EVA/SiO2/Al2O3, were synthesized by γ-irradiation and the highest gel content of 81.2–95.3% was achieved at 30 kGy. The physicochemical properties of EVA-based nanocomposites were characterized by FT-IR, XRD, DSC and SEM techniques. Usage of irradiated EVA and EVA-based nanocomposites for treatment of CF by coating technique was successfully achieved. This technique provides a simple and versatile method leading to excellent uniform and smooth surface morphology without aggregation. The weight gain, mechanical properties, thermal properties, water vapor permeability and flame-retardant properties of the modified CF were evaluated. Moreover, compared with control CF, the resistivity of water absorptivity and hydrophobic property and the thermal stability were gained. The flame retardant properties of CF samples were performed using limited oxygen index (LOI) and vertical burning flame tests. LOI percentages of CF/EVA/SiO2, CF/EVA/Al2O3 and CF/EVA/SiO2/Al2O3 increased to 25.3, 27.5, and 29.3%, respectively. Untreated CF ignited and burned rapidly after 5 s. Meanwhile, the treated CF hold flame resistance properties and the burning time prolonged to 25 s. The results of the treated CF providing revealed hydrophobic and protective capability of the fabrics from being destroyed by burning, and support their further use in waterproof and flame retardant applications of fabrics.

Performance Improvement of PVDF-HFP-Based Gel Polymer Electrolyte with the Dopant of Octavinyl-Polyhedral Oligomeric Silsesquioxane

Gel polymer electrolytes have the advantages of both a solid electrolyte and a liquid electrolyte. As a transitional product before which a solid electrolyte can be comprehensively used, gel polymer electrolytes are of great research value. They can reduce the risk of spontaneous combustion and explosion caused by leakage during the use of conventional liquid electrolytes. Poly(vinylidene-fluoride-co-hexafluoropropylene) (PVDF–HFP), a material with excellent performance, has been widely utilized in the preparation of gel polymer electrolytes. Here, PVDF–HFP-based gel polymer membranes with polyvinyl pyrrolidone (PVP) pores were prepared using a phase inversion method, and Octavinyl-polyhedral oligomeric silsesquioxane (OVAPOSS) was doped to improve its temperature resistance as well as its ionic conductivity, to enhance its safety and electrochemical performance. The final prepared polymer membrane had a porosity of 85.06% and still had a certain mechanical strength at 160 °C without any shrinkage. The gel polymer electrolyte prepared with this polymer membrane had an ionic conductivity of 1.62 × 10⁻³ S·cm⁻¹ at 30 °C, as well as an electrochemical window of about 5.5 V. The LiCoO₂-Li button half-cell prepared therefrom had a specific capacity of 141 mAh·g⁻¹ at a rate of 1C. The coulombic efficiency remained above 99% within 100 cycles and the capacity retention rate reached 99.5%, which reveals an excellent cycling stability.

A Review of Functional Separators for Lithium Metal Battery Applications

Lithium metal batteries are considered “rough diamonds” in electrochemical energy storage systems. Li-metal anodes have the versatile advantages of high theoretical capacity, low density, and low reaction potential, making them feasible candidates for next-generation battery applications. However, unsolved problems, such as dendritic growths, high reactivity of Li-metal, low Coulombic efficiency, and safety hazards, still exist and hamper the improvement of cell performance and reliability. The use of functional separators is one of the technologies that can contribute to solving these problems. Recently, functional separators have been actively studied and developed. In this paper, we summarize trends in the research on separators and predict future prospects.

Enhancement of the electrochemical performance of lithium-ion batteries by SiO2@poly(2-acrylamido-2-methylpropanesulfonic acid) nanosphere addition into a polypropylene membrane

Employing electrostatic self-assembly and free radical polymerization, the surface of SiO₂ nanospheres was coated with poly(2-acrylamido-2-methylpropanesulfonic acid) (SiO₂@PAMPS) bearing strong electron withdrawing sulfonic and amide groups, enhancing the dissociation ability of the lithium salt of the liquid electrolyte and absorbing anions via hydrogen bonds. After SiO₂@PAMPS nanospheres were introduced into the polypropylene (PP) membrane (SiO₂@PAMPS/PP), the electrolyte affinity and electrolyte uptake of the composite separators were significantly improved. The ionic conductivity of SiO₂@PAMPS/PP-18% (where 18% represents the concentration of the solution used for coating) soaked in liquid electrolyte was even 0.728 mS cm^-1 at 30 °C, much higher than that of the pristine PP membrane. The LiFePO₄/Li half-cell with SiO₂@PAMPS/PP-18% had a discharge capacity of 148.10 mA h g^-1 and retained 98.67% of the original capacity even after 120 cycles at 0.5C. Even at a rate of 1.0C, the cell capacity could be maintained above 120 mA h g^-1. Therefore, a coating formula was developed that could considerably improve the cycling ability and high rate charge-discharge performance of lithium ion batteries.

Structural Properties and Catalytic Activity of Binary Poly (vinyl alcohol)/Al2O3 Nanocomposite Film for Synthesis of Thiazoles

A solution casting technique was applied to prepare a binary poly (vinyl alcohol)/Al2O3 nanocomposite. The structural properties of nanocomposite were investigated using Fourier-transform infrared spectra, field emission scanning electron microscope, energy dispersive X-ray analyses, and X-ray diffraction. The hybrid PVA/Al2O3 film exhibited a conspicuous catalytic performance for synthesis of thiazole derivatives under mild reaction conditions. Moreover, the optimization of catalytic efficiency and reusability of this nanocomposite have been investigated.

Crystalline Al2O3 modified porous poly(aryl ether ketone) (PAEK) composite separators for high performance lithium-ion batteries via an electrospinning technique

The thermostability and wettability of a separator play key roles in improving the safety and electrochemical properties of lithium-ion batteries (LIBs).